Antenna system



May 2, 1961 H. C. KENDALL ET-AL ANTENNA SYSTEM Original Filed Aug. 19,1953 FIG.

5 Sheets-Sheet 1 INVENTORS C.KENDALL AND H.AUER JR.

THEI- ATTORNEY y 1961 H. c. KENDALL ET AL 2,982,962

ANTENNA SYSTEM 3 Sheets-Sheet 2 Original Filed Aug. 19, 1953 FIG. 2.

INVENTORS H. C. KENDALL AND J. H. AUER JR.

7 THEIR ATTO y 2, 1961 H. c. KENDALL ET AL 2,982,962

ANTENNA SYSTEM Original Filed Aug. 19, 1953 3 Sheets-Sheet 5 INVENTORS KE N DALL AN D C. BY H. AUER JR.

THEIR ATTORNEY "United States Patent 2,982,962 ANTENNA SYSTEM Hugh 'C.Kendall and John H. Auer, Jn, Rochester, N.Y., assignors to GeneralRailway Signal Company, Rochester, N.Y.

Original application Aug. 19, 1953, Ser. No. 375,192,

now Patent No. 2,805,335, dated Sept. 3, 1957. Divided and thisapplication June 12, 1957, Ser. No. 665,185 r 1 Claim. (Cl. 343-840)This invention relates to apparatus for measuring the speed of movingobjects, and more particularly pertains to transmitting and receivingapparatus for measuring the speeds of moving vehicles according to theDoppler frequency shift of a high frequency radio signal. The presentapplication is a division of our copending application, Ser. No.375,192, filed August 19, 1953, now Patent 2,805,335, and no claim isintended to be made herein to subject matter disclosed and claimed insuch prior application.

The apparatus of this invention is especially useful in measuring thespeeds of railway cars as they pass through the car retarders of arailway hump classification yard. In such a yard, the cars are pushedover the crest of a hump and then allowed to roll either singly or incuts of two or more cars down the hump and over a plurality of routeselecting switches to a particular one of a number of classificationtracks selected according to the car's destination.

As each car or cut of cars rolls down the slope of the bump, it passesthrough a plurality of car retarders, each of which is selectivelycontrollable as to the braking force it exerts on the wheels of each carand also the length of time such force is'applied. In this way, thespeeds of the cars can be properly controlled so that they will entertheir destination tracks at the proper speed and couple to the carsalready in such track at a low speed, thereby avoiding damage to thecars and their contents. Systems of this kind wherein the car retardersare automatically controlled according to the weight, destination, andspeed of the cars are disclosed in the copending applications of N. C.L. Brown, Ser. No. 359,052, filed June 2, 1953, and of N. B. Coley, Ser.No. 359,069, filed June 2, 1953, both assigned to the assignee of thepresent application.

In such systems for automatically controlling the retarder of a carclassification yard as disclosed in these prior applications,information as to the speed of the cars as they pass through the carretarders is preferably provided by means of an organization known as aninterferometer or continuous-wave radar, one of which is associated witheach carretarder. This apparatus includes transmitting and receivingequipment which may be located between the track rails near the exit endof a retarder and is eflect-ive to cause a beam of high frequency radioenergy to be constantly transmitted toward approaching vehicles. Aportion of, such transmitted energy is reflected from the approachingvehicle back to the receiving. apparatus with a slightly higherfrequencythan the transmitted signal, and this frequency shift is proportionalto-the velocity of the approaching car in accordance with the Dopplerprinciple.

By mixing a portion of the transmitted signalwith the reflected signalof higher frequency that is received, a beat frequency signal may beextracted Whosefrequency equals the Doppler frequency. By providingapparatus which is distinctively responsive to the frequencyvalue ofthis beat frequency signal, the speeds of approaching vehiclesarecontinually and accurately determined. A

circuit organization for accomplishingthis function-is dis closed andclaimed in the prior co -pending application of H. C. Kendall and J. H.Auer, In, Ser. No.- 359,162,. filed June 2, 1953.

An object of this invention is to provide a reflecting horn common toboth transmitting and receiving antennas f an interferometer.

An additional object of this invention is to provide a common reflectinghorn for both transmitting and receiving functions having a jackassociated with the receiving antenna into which a plug may be insertedfor metering purposes and with said jack so mounted in the reflectinghorn with respect to the receiving antenna that improved I transmittingcharacteristics result 4 j V Other objects, purposes, and characteristicfeatures of this invention will in part be obvious from the accompanyingdrawings and in part pointed out as the description of the inventionprogresses. e In the description of the invention, reference will madeto the accompanying drawings in which like'refer; ence charactersdesignatecorresponding parts in the 'several views and in which: T Fig.1illustrates the housing in which the-transmitting and receivingapparatus of this invention is mounted;

Fig. 2 illustrates the common reflecting horn and the associatedtransmitting antenna, receiving antenna and reentrant cavity resonator;

Fig. 3 illustrates a portion of the apparatus of Fig.2 but with areflecting shield in place in front oftheantennas was to produce thedesired radiation pattern;

Fig. 4 is an enlarged sectional view of the structul' e' of Fig.2showing in detail both transmitting and receiv; ing antennas and thereentrant type cavity resonaton Fig. 1 includes a view of the housing 10for the appa ratus shown on Fig. 2. This housing 10 is provided with ahinged cover 11 which is held in position by the bolt 12. The housing isfastened to the pedestal 13 by means of bolts such as those shown'at 14and 1513 The pedestal 13 is fastened to a support which may bepositioned" between the track rails near the exit end of a retarder, bybolts which pass through the mounting'holes shown in the base of thispedestal 13. The casting of which this housing 10 is made is providedwith openings over which are placed sheets 16 of a fibrous glassmaterial which'is effective to seal the housing against the entranceofdirt and moisture but will still allow high frequency radio energy tobe directed out of the housing '10 towards approachingvehicles.

Fig. 2 comprises a view of the common reflecting horn 17 used for bothreceiving and transmitting antennas. This view also shows thetransmitting antenna A and receiving antenna B, both of which aremountedwithin the space enclosedby the surfaces of the parabolic reflectinghorn. Onthe bottom sideof the shelf 18, whose upper surface comprises-aportion of the reflecting horn, is mounted, by means of clamps 25, areentrant type of cavity resonator 24 which provides the high frequencyoscillations that are transmitted toward approaching vehicles. A portionof a metering jack J is shown mounted in the uppersurface 20. 7

High frequency energy reflected from a target and intercepted by thereceiving antenna B is rectified'bya crystal rectifier 51 shown in Fig.-4 and the resulting beat frequency is thentransferred over the shieldedcable 22 to various other electrical components mounted on the lowersurface 18. This shielded cable has its shield grounded by beingconnected to the terminal 23 which is connected directly to the horn 17.In practice other electrical components and devices-suchaselectrontubes, transformers, resistors, and the like, may be-mounted onthe shelf 21 and also on the bottom surface of'shelf 18 although'thesecomponents have not been illustrated {in Fig. 2.

Fig. 3 illustrates a portion of the horn of-Fig. 2, showing particularlythe way in which a reflecting shield 30 is mounted over the frontopening of. the horn directly in front of the antennas A and B. Thisreflecting; shield 30 prevents high frequency energy from being radiateddirectly from the transmitting antenna A toward the target. Energyradiated from this antenna A which strikes the reflecting shield 30 isreflected back to the horn and then again reflected. from the backsurface 31 of the horn, thereby causing energy to be transmitted in thedesired pattern along the axis of the parabolic back surface 31. ThisFig. 3 also shows the protecting cover 32 in place. This cover is shownremoved in Fig. 2 so that the cavity resonator 24 can more clearly beseen.

Fig. 4 is a sectional view of the apparatus shown in Fig. 2. Thissectional view is taken on a vertical plane through both thetransmitting and receiving antennas A and B, respectively. In this Fig.4, the transmitting antenna A is shown as comprising what is known as .afolded quarter-wave ground plane antenna. The circular disc 35 formingthe ground plane is soldered to the sleeve 36. Inside this sleeve 36 isan insulating bushing 37 having a hollow core in which is inserted aprobe 38. This probe 38,is threaded at its upper end into the bent overportion 39 of the sleeve 36. The sleeve 36 extends through a clearancehole in the shelf 18 and is threaded into a boss 40 on the cavityresonator 24. The lower end of the probe 38 thus extends directly intothe cavity 24 so that high frequency energy is coupled directly to thetransmitting antenna A. The amount of coupling of the probe 38 to thecavity 24 is adjustable by rotating the threaded sleeve 36 in the boss40 so as to vary the amount by which the lower end of the probe extendsinto the cavity 24. The desired coupling adjustment is maintained by alock nut 41. The use of a ground plane as provided by the disc 35permits varying the coupling of the probe to the cavity without varyingthe distance by which the folded quarter-wave antenna extends above itsassociated ground plane.

The receiving antenna B is also a quarter-wave antenna with the uppersurface of the horn acting as its counter- 'poise. This antennacomprises a cylindrical radiator 45 having a soldering ing 46 fastenedthereto, with the upper end of the radiator inserted into a hole in theinsulating bushing 47. The soldering lug abuts against a shoulder on theradiator 45. Both insulating bushing 47 and lug 46are held in place onthe end portion of radiator 45 by spinning over the rim 50 of theradiator 45. The bushing 47 is held in place in the sleeve 48 by causingthe rim 49 of the sleeve 48 to be spun over the bushing 47.

The sleeve 48 has its outer surface threaded so as to -fit into athreaded hole in the upper surface of the refleeting horn 20. The sleeve48 is provided with an opening into which fits a crystal rectifier 51,one end of which is seated in a hole drilled into the upper end of theradiator 45. The radiator 45 is, of course, insulated from the sleeve 48by the insulating bushing 47.

A nut 52, threaded both on the inside and outside, fastens over theupper threaded portion of the sleeve 48 to thereby lock the sleeve inthe desired position with respect to the upper surface of the born 20. Acap 53, threaded on the inside, screws onto the nut 52 and causes aspring 54 to exert pressure on the crystal 51 so that it will bemaintained in proper contact with the radiator 45, and also insure thatits upper end is connected to the upper surface of the horn 20 which isat ground potential. The signal received by this receiving antenna B andrectified by the crystal rectifier is coupled to an associatedpreamplifier by means of a connection made to the terminal 46.

A metering jack J is also mounted through the upper surface of the horn20. This jack is associated electrically with the receiving antenna insuch a manner as to permit measuring the current through a resistor (notshown) that is connected in parallel with the crystal" recti- 4 fier 51.This jack J comprises a bushing 61 which is inserted through a hole inthe upper surface of the horn 20, and secured by means of a nut 62 whichis screwed onto the outer threaded portion of the member 61 extendingabove the upper surface of the horn 20. A metal washer 63 may be used,if desired, between the bushing 61 and the bottom surface to preventrotation of the jack I as the nut, 62 is tightened.

-A connection made to the terminal 68 is ordinarily completed throughthe closed contacts 66 and 67 to the terminal 65, which is grounded tohorn 17. Such a circuit connection is ordinarily made in series with theabove-mentioned resistor so that the current passing through theresistor also .passes through the abovedescribed circuit provided by thejack J.

When a plug is inserted through the opening in the bushing 61, the tipof such plug pushes against the spring like member 69 so as to open theseries circuit at contacts 66 and 67, and the sleeve of such plug thenmakes contact with member 61. A current meter having its terminalsconnected respectively to the sleeve and tip of such plug will then haveflowing through its Winding the current desired to be measured. Thiscurrent will flow through the meter rather than through the previouslydescribed circuit provided by the jack which is now open circuited.

It has been found that the jack I should preferably be located directlybehind the receiving antenna B and with a distance between jack andantenna approximating a quarter-wave length of the frequency used in theinterferometer system. When these conditions are fulfilled, it is foundthat the jack J providesthe effect of acting as a parasitic element withrespect to the receiving antenna. As a result, the apparent gain of thereceiving antenna B is increased so that a high output is obtained fromthe antenna for a given amplitude of reflected signal.

Having described an interferometer structure and related apparatus asone specific embodiment of this invention, we desire it to be understoodthat this form is selected merely to illustrate the principles of thisinvention and that other embodiments, adaptations, and modifications maybe employed without departing from the spirit or scope of thisinvention.

What we claim is:

An antenna system comprising, a reflecting horn having parallel planetop and bottom surfaces and a back surface following a parabolic curve,a longitudinal receiving antenna disposed in said top surface at thefocus of said parabolic surface and being supported in a positionextending longitudinally normal to said top and bot tom surfaces withinsaid horn, and a longitudinal metering jack adapted to receive a plughaving independent meter connections, said jack being disposed in saidtop surface and extending within said horn at a point along the axis ofsaid parabolic curve of said back surface between said receiving antennaand said back surface, the distance between said receiving antenna andsaid jack being substantially one quarter wave length of the operatingfrequency to be received, whereby said metering jack serves both as adetachable coupling means for the attachment of a meter and as a meansfor increasing the gain of the receiving antenna.

References Cited in the file of this patent UNITED. STATES PATENTS2,054,896 Dallenbach Sept. 22, 1936 2,112,282 -Fritz Mar. 29, 19382,430,568 Hershberger Nov. ll, 1947 2,494,691 Cork et al. Jan. 17, 19502,539,680 Wehner Jan. 30, 1951 2,825,062 Chu et al. Feb. 25, 1958FOREIGN PATENTS 53,193 France Dec. 4, 1944

